20 AN.\r.\L Ki:i'()irrs of i »i;i'AK'i-.Mi:N'r of a<;ui(TI/i fkf. vsm 
For ihv lirsf tiiii*' in niiiny y»':irs the «'ast<'rM si»nu-(' bi'ctlc roMchcd outbreak 
proportions in several areas in New Kii^'land and New York. On tlie recom- 
mendation of the Bureau the land-nianajjlnj; ap:«Mi<ies have work under way 
to control this outbreak on sonn? 22.(MM) acres in tlie (ire**!! Moimiain National 
Forest and adjacent privately owned lands. 
On the advice and under the technical supervision of the Bureau, the Forest 
Service is continuinj; the effort to control the outbreak of the forest tent cater- 
pillar in recreational areas in the Lake States. 
RESEARCH ACTIVITIES 
E3T-'ECTS OF CLIMATIC ON P.AKK BE3 Tr.ES 
F»)llowin.2r the purchase of now low-temperature efpiipment at three of our 
western stations, the laboratory study of the effects of extreme cold upon the 
brood of pine bark be<Ules was considerably expanded. Pertinent facts .so far 
establislKHl may be stated as follows: (1) Of the three most destructive western 
bark beetles the brood of the western pine beetle is least resistant to low tempera- 
tures, that of the Black Hills beetle is most resistant, while that of the mf>untam 
pine beetle is intermediate. (2) A sjx^cies occurring in warmer parts of its 
range is less resistant to low temperatures than the same species in colder 
areas. (3) Bark beetle brood is less resistant to nnseasonal)ly low tempera- 
tures in tli(^ fall and early in the spring than to similar temperatures during the 
dead of winter, because of an establishiiient of "c(jld hardiness." (4) There 
are strong indications that individuals of the same species of bark beetle reared 
in the same area vary consideral)ly as regards resistance to low temperatures 
according to the host tree in which they occur. (5) Some work upon the rela- 
tion of the water and the lipoid contents of the body to cold hardiness has been 
begun but has not yet reached definite conclusions. 
Something of the relation of drought periods and outbreaks of the western 
pine beetle has been known for some time. The frequency of drought ix^riods 
in the Pacific Northwest has been studied through an analysis of tree rings 
and growth fluctuations covering the last 6oO years. 
PEXErrRATTNG OIL FOR CONTROL OF BARK BEiri LES 
For .several years experiments with the use of penetrating oils in the control 
of bark beetles in sugar pine and ponderosa pine were conducted in California 
with more or loss erratic results due to the thickness of the bark in these trees. 
However, the results were so excellent, where penetration was obtained, that 
it was decided to move these experiments to Coeur d'Alene and try the method 
out on bark beetles in the thinner barked lodgepole pine. The use of this 
method permits control work to i)rocee(l during .seasons of high lire hazard. 
Definite progress has l)een made, but considerable experimental work is still 
needed to determine what factors, such as temperature, moisture et'iitent of 
bark, etc., are conducive to success. 
IN.TKCTION OF CUF.MICATS INIO THF.KS 
Experiments with the introduction of chemicals into the sap stream of trees 
was begun as a i)romising method of controlling bark b(>etles. The early work 
was done larg(>ly at Ashevill(>. N. C. It has been applied on a fairly large scale 
in several experimental control operations in tlu> northern Rocky Mountains 
and has provKl very successful in tre(vs which have not been infi>ste<l so long 
that the water conduction has hoou seriously affected by the d«'velopmcnt of the 
blue stain fungus. 
Living trees can also be injected with cojjper sulphate <>)• other pres(>rvat ives, 
which kill the tree and prevent later insiH't attack. Such material can then 
be used in rustic work or otherwise without injury from insect attack. Tree 
injection has been i)ut to another use in the eradication cami»aign .Mg.ainst the 
Dutch elm disease, where a modilication of the method is used to kill elm trees 
jind render them unsuitable for the attack and development of bark becMles which 
;ict as \cetors of the disease organism. 
WHITE GRUBS IN NURSERIES AND PLANTATIONS 
Further investigations upon metliods of treating the soil in forest nurseries 
8o as to prevent later infestation ha\(' shown that all methods tints far tricnl 
